1. Field of Inventions
The present inventions relate generally to medical devices that support one or more diagnostic or therapeutic elements in contact with body tissue and, more particularly, to medical devices that support one or more diagnostic or therapeutic elements in contact with bodily orifices or the tissue surrounding such orifices.
2. Description of the Related Art
There are many instances where diagnostic and therapeutic elements must be inserted into the body. One instance involves the treatment of cardiac conditions such as atrial fibrillation and atrial flutter which lead to an unpleasant, irregular heart beat, called arrhythmia.
Normal sinus rhythm of the heart begins with the sinoatrial node (or xe2x80x9cSA nodexe2x80x9d) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or xe2x80x9cAV nodexe2x80x9d). This propagation causes the atria to contract in an organized way to transport blood from the atria to the ventricles, and to provide timed stimulation of the ventricles. The AV node regulates the propagation delay to the atrioventricular bundle (or xe2x80x9cHISxe2x80x9d bundle). This coordination of the electrical activity of the heart causes atrial systole during ventricular diastole. This, in turn, improves the mechanical function of the heart. Atrial fibrillation occurs when anatomical obstacles in the heart disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called xe2x80x9cconduction blocksxe2x80x9d) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called xe2x80x9creentry circuits,xe2x80x9d disrupt the normally uniform activation of the left and right atria.
Because of a loss of atrioventricular synchrony, the people who suffer from atrial fibrillation and flutter also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are also at greater risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
One surgical method of treating atrial fibrillation by interrupting pathways for reentry circuits is the so-called xe2x80x9cmaze procedurexe2x80x9d which relies on a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits. The maze procedure has been found very effective in curing atrial fibrillation. However, the maze procedure is technically difficult to do. It also requires open heart surgery and is very expensive.
Maze-like procedures have also been developed utilizing catheters which can form lesions on the endocardium (the lesions being 1 to 15 cm in length and of varying shape) to effectively create a maze for electrical conduction in a predetermined path. The formation of these lesions by soft tissue coagulation (also referred to as xe2x80x9cablationxe2x80x9d) can provide the same therapeutic benefits that the complex incision patterns that the surgical maze procedure presently provides, but without invasive, open heart surgery.
Catheters used to create lesions typically include a relatively long and relatively flexible body portion that has a soft tissue coagulation electrode on its distal end and/or a series of spaced tissue coagulation electrodes near the distal end. The portion of the catheter body portion that is inserted into the patient is typically from 23 to 55 inches in length and there may be another 8 to 15 inches, including a handle, outside the patient. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the interior of the heart, and then manipulated such that the coagulation electrode contacts the tissue that is to be ablated. Fluoroscopic imaging is used to provide the physician with a visual indication of the location of the catheter.
In some instances, the proximal end of the catheter body is connected to a handle that includes steering controls. Exemplary catheters of this type are disclosed in U.S. Pat. No. 5,582,609. In other instances, the catheter body is inserted into the patient through a sheath and the distal portion of the catheter is bent into loop that extends outwardly from the sheath. This may be accomplished by pivotably securing the distal end of the catheter to the distal end of the sheath, as is illustrated in co-pending U.S. application Ser. No. 08/769,856, filed Dec. 19, 1996, and entitled xe2x80x9cLoop Structures for Supporting Multiple Electrode Elements.xe2x80x9d The loop is formed as the catheter is pushed in the distal direction. The loop may also be formed by securing a pull wire to the distal end of the catheter that extends back through the sheath, as is illustrated in U.S. Pat. No. 5,910,129, which is incorporated herein by reference. Loop catheters are advantageous in that they tend to conform to different tissue contours and geometries and provide intimate contact between the spaced tissue coagulation electrodes (or other diagnostic or therapeutic elements) and the tissue.
Mapping baskets, which may be carried on the distal end of separate mapping catheters, are often used to locate the reentry pathways prior to the formation of lesions. Exemplary mapping baskets are disclosed in U.S. Pat. No. 5,823,189. Additionally, once the lesions have been formed, the mapping baskets are again used to determine whether the lesions have successfully eliminated the reentry pathways. Mapping baskets are superior to conventional diagnostic catheters because mapping baskets do not need to be steered to a variety of sites within a bodily region such as the pulmonary vein during a diagnostic procedure and, instead, can perform a diagnostic procedure in a single beat from a single location.
The use of a mapping catheter in combination with a soft tissue coagulation catheter can, however, be problematic. For example, when a mapping catheter is used in combination a soft tissue coagulation catheter, a pair of transseptal punctures (or a single relatively large puncture) must be formed in the atrial septum so that the catheters can be advanced from the right atria, through the fossa ovalis and into the left atria. Two punctures (or a relatively large single puncture) must also be formed in the femoral vein. In addition, the time required to manipulate two catheters into their respective positions can lead to prolonged periods of fluoroscopy.
The issues associated with the combined use of mapping and coagulation catheters notwithstanding, one lesion that has proven to be difficult to form with conventional catheters is the circumferential lesion that is used to isolate the pulmonary vein and cure ectopic atrial fibrillation. Lesions that isolate the pulmonary vein may be formed within the pulmonary vein itself or in the tissue surrounding the pulmonary vein. Conventional steerable catheters and loop catheters have proven to be less than effective with respect to the formation of such circumferential lesions. Specifically, it is difficult to form an effective circumferential lesion by forming a pattern of relatively small diameter lesions.
Accordingly, the inventors herein have determined that a need exists for a device that is capable of both mapping and coagulating tissue. The inventors herein have further determined that a need exists generally for structures that can be used to create circumferential lesions within or around bodily orifices. The inventors herein have also determined that a need exists for a device that can both map the pulmonary vein and create lesions within or around the pulmonary vein.
Accordingly, the general object of the present inventions is to provide a device that avoids, for practical purposes, the aforementioned problems. In particular, one object of the present inventions is to provide a device that can be used to create circumferential lesions in or around the pulmonary vein and other bodily orifices in a more efficient manner than conventional apparatus. Another object of the present invention is to provide a device that can be used to both map the pulmonary vein and create lesions within or around the pulmonary vein.
In order to accomplish some of these and other objectives, a probe in accordance with one embodiment of a present invention includes a support body, an expandable/collapsible tissue coagulation structure supported on the support body, and a mapping structure. The mapping structure may be supported on the support body distally of the expandable/collapsible tissue coagulation structure or, alternatively, passable through a lumen in the support body so that it can be advanced beyond the distal end of the support body. Such a probe provides a number of advantages over conventional apparatus. For example, the combination of the tissue coagulation structure and the mapping structure allows the physician to perform a mapping and coagulation procedure with a single instrument, thereby eliminating the aforementioned problems in the art. The mapping structure may also be positioned within the pulmonary vein or other orifice during a coagulation procedure and serve as an anchor to improve the accuracy of the placement of the coagulation structure. Additionally, the expandable tissue coagulation structure is especially useful for creating circular lesions in and around the pulmonary vein and other body orifices.
In order to accomplish some of these and other objectives, a probe in accordance with one embodiment of a present invention includes a support body defining a longitudinal axis, an expandable/collapsible hoop structure defining an open interior region and supported on the support body, at least one operative element supported on the expandable/collapsible hoop structure. Such a probe provides a number of advantages over conventional apparatus. For example, in an implementation where the operative element consists of a plurality of spaced electrodes, the hoop structure can be readily positioned such that the electrodes are brought into contact with tissue in or around the pulmonary vein or other bodily orifice. The hoop structure also defines an open region that allows blood or other bodily fluids to pass therethrough. As a result, the present probe facilitates the formation of a circumferential lesion without the difficulties associated with conventional apparatus and does so without the occlusion of blood or other fluids.
The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.